Editing Glasses (section)

== Corrective lens shape ==
[[File:Brille eingeklappt (fcm).jpg|thumb|Modern glasses with a rectangular lens shape]]

Corrective lenses can be produced in many different shapes from a circular lens called a lens blank.  Lens blanks are cut to fit the shape of the frame that will hold them. Frame styles vary and fashion trends change over time, resulting in a multitude of lens shapes. For lower power lenses, there are few restrictions, allowing for many trendy and fashionable shapes. Higher power lenses can distort [[peripheral vision]] and may become thick and heavy if a large lens shape is used. However, if the lens is too small, it can drastically reduce the field of view.

[[Bifocals|Bifocal]], [[Trifocal lenses|trifocal]], and [[progressive lens]]es generally require a taller lens shape to leave room for the different segments while preserving an adequate field of view through each segment. Frames with rounded edges are the most efficient for correcting [[myopia|myopic]] prescriptions, with perfectly round frames being the most efficient. Before the advent of eyeglasses as a fashion item, when frames were constructed with only functionality in mind, virtually all eyeglasses were either [[Windsor glasses|round]], [[oval]], panto, [[rectangular]], [[octagonal]], or [[square]]. It was not until glasses began to be seen as an accessory that different shapes were introduced to be more aesthetically pleasing than functional.